Peel Browning Research Articles

Low voltage electrostatic field combined with ice-temperature to improve the quality of litchi during storage

Litchi is popular among consumers due to its delicious taste, however, the extremely short shelf life limits its commercial value. Few studies have been conducted to develop new technologies to extend the shelf life of litchi. Therefore, this study applied a novel technique (low voltage electrostatic field, LVEF) combined with ice-temperature (0 °C) treatment on litchi and evaluated its quality characteristics during storage. The results demonstrated that low voltage electrostatic field with ice-temperature storage (LVEF-IT) decreased malondialdehyde content, relative electrolyte leakage, and polyphenol oxidase and peroxidase activities, successfully delayed the start of peel browning. Additionally, it preserved the fruit pulp’s excellent quality, which included high concentrations of soluble solids, ascorbic acid, and soluble protein. These findings imply that LVEF-IT treatment may be a novel technique for extending the storage time of litchi.

Synergistic modulation of oxidative peel browning in postharvest litchi through ultrasound and salicylic acid coupling

Pericarp browning in litchi is a major postharvest problem that drastically affects cosmetic appeal and marketability of fruits. This study explores the efficacy of postharvest treatments involving ultrasound (US) combined with salicylic acid (SA) in mitigating oxidative browning and preserving quality attributes during ambient storage. Results indicate that the combined treatment of US and SA, particularly at a concentration of 2 mM, effectively reduced weight loss, decay incidence, and the production of reactive oxygen species. Furthermore, this combination maintained higher levels of total soluble solids, titratable acidity, phenolic content, antioxidants, and phenylalanine ammonia-lyase activity while suppressed polyphenol oxidase activity. The combined US + SA (2 mM) synergistically delayed the quality deterioration and pericarp browning in litchi during storage.

Preserving functional properties and inhibiting postharvest peel browning in guava during cold storage via 24-epibrassinolide application

Postharvest peel browning is one of the primary issues accountable for the subdued consumer acceptability and market value of guava fruit. However, postharvest treatment with brassinosteroid can reduce the peel browning to some extent through various modes of action. In current study, the influence of exogenous 24-epibrassinolide (EBL) application on antioxidant system and chilling injury (CI) characteristics of guavas during cold storage at 10 ± 1 ℃ were assessed. The mature green fruit exposed to various concentrations (15, 30, 45, 60 and 75 µg kg−1) of EBL displayed a notably lower fruit weight loss, respiration rate, electrolyte leakage and CI index, while higher consumer acceptability. Further, treatment with EBL has recorded lower amassing of hydrogen peroxide and malondialdehyde by suppressing lipoxygenase activity. Postharvest EBL application also heightened the content of total phenolics, ascorbic acid, total flavonoids and total antioxidant capacity. The enhanced activities of ascorbate peroxidase, catalase, superoxide dismutase and peroxidase due to EBL application impede the burst of reactive oxygen species. Moreover, correlation and regression analysis of tested biochemical parameters including enzymatic and non-enzymatic antioxidants exhibited a strong association and contributed 98.24–99.88 % variability in fruit weight loss, respiration rate, electrolyte leakage, CI index and consumer acceptability. Among different concentrations tested, 60 µg kg−1 EBL-treated guavas exhibited the desirable qualities and least CI index. From the study, it is concluded that the novelty of EBL can be gainfully harnessed in a postharvest handling system to induce cold tolerance and widen the storage life of cold-stored guava fruit.

Pre-storage melatonin treatment maintains cell membrane integrity, reduces fruit browning and decay incidence in guava (Psidium guajava)

An experiments were conducted during 2021–22 at ICAR-Indian Agricultural Research Institute, New Delhi to study the impact of melatonin (MT) on key characteristics of guava (Psidium guajava L. cv. Barafkhana). Guava fruits were treated with different MT concentrations (200, 400, 600 and 800 μM) and stored at 10±1°C with 85–90% RH. The research revealed that treating with 600 μM MT notably decreased polyphenoloxidase activity by 57%, leading to delayed peel browning and also suppressed polygalacturonase (PG) activity by approximately 45% and pectine methylesterase activity by about 73%, resulting in higher firmness (5.33 N). Following a 20-days period of cold storage, significant reductions in electrolyte leakage, hydrogen peroxide accumulation and lipoxygenase activity were observed, thereby preserving cell membrane integrity. Additionally, MT stimulated the antioxidant defense system, boosted proline content accumulation, and enhanced phenylalanine ammonia-lyase activity. Together, these effects contributed to enhanced resistance against postharvest fungal decay (8.75%). In conclusion, MT at a concentration of 600 μM proves to be an effective postharvest treatment for maintaining texture, reducing fruit decay and extending the shelf-life of guava during cold storage.

Effects of Different Pre-Harvest Bagging Times on Fruit Quality of Apple.

Pre-harvest bagging can improve fruit color and protects against diseases. However, it was discovered that improper bagging times could lead to peel browning in production. Using the Ruixue apple variety as the research model, a study was conducted to compare the external and internal quality of fruits bagged at seven different timings between 50 and 115 days after full bloom (DAFB). Our findings indicate that delaying the bagging time can reduce the occurrence of peel browning in Ruixue apples. Compared to the control, the special bag reduced the browning index by 22.95%. However, the fruit point index of Ruixue fruits increased by 65.05% at 115 DAFB compared to 50 DAFB when bagging was delayed. The chlorophyll content of Ruixue fruits in special bags generally increased and then decreased, with the highest chlorophyll content of Ruixue fruits in special bags at 90 DAFB, which was 26.02 mg·kg-1. When the bagging process was delayed, the soluble solids, total phenols, and flavonoids content in the fruits increased, while the number of control volatiles decreased by 10. After two years of testing, results show that using special fruit bags at 90 DAFB bagging can significantly improve the fruit quality of Ruixue apple.

Low oxygen concentration alleviates banana peel browning by inhibiting membrane lipid oxidation and polyphenol oxidase activity

SummaryBananas, a common fruit in our daily diet, often develop physiological disorders during the late ripening period, resulting in browning, which reduces their suitability for consumption. In this study, we inhibited the browning phenomenon by reducing the oxygen concentration to improve their storage period. Compared with banana fruit treated with high oxygen concentration, banana fruit treated with low oxygen concentration had higher hardness and significantly delayed weight loss. The analysis showed that low oxygen concentration enhanced the antioxidant capacity of banana skin cells by maintaining the DPPH scavenging capacity of antioxidant substances in the banana peel. The activity of the membrane‐degrading enzyme LOX is reduced, and the permeability of the cells is reduced, thus maintaining the structural integrity of the cells. Scanning electron microscope analysis showed that the integrity of the cell membrane was well maintained under low oxygen concentration, which restricted the reaction of phenols and PPO enzymes to produce quinones under the action of oxygen, and inhibited the browning phenomenon. These results suggest that low oxygen concentrations inhibit banana Browning by maintaining the structural integrity of cell membranes.

Enhancement of antioxidant quality by Bacillus siamensis N-1 and the role of LcPOD4 in regulating peel browning and senescence of litchi fruit

Plant peroxidases (POD) are involved in various physiological and biochemical processes. Currently, there are relatively few studies on the role of POD in regulating the antioxidant capacity and senescence of postharvest litchi. In this study, we assessed the effects of Bacillus siamensis strain N-1 on the physiology and antioxidant quality of litchi fruit stored at 25 ℃, and characterized the molecular function of LcPOD4 gene in regulating the senescence of litchi fruit. The results showed that N-1 treatment significantly suppressed the increase in ethylene production, electrolyte leakage, and malondialdehyde (MDA) but did not inhibit the respiration rate of litchi during storage. Meanwhile, N-1-treated fruit maintained higher levels of phenolics, flavonoids, and total antioxidant capacity (T-AOC) and lower levels of superoxide anions (O2-.) and hydrogen peroxide (H2O2). In addition, N-1 treatment enhanced the activity of defense enzymes, including superoxide dismutase (SOD), peroxidase (POD), glutathione reductase (GR), and phenylalanine ammonia-lyase (PAL). The results of quantitative real-time PCR (qRT-PCR) showed that the expression of nine selected LcPOD genes was induced by N-1 treatment at later stages of litchi storage. LcPOD4 cloned from litchi fruit was located in the cell wall and membrane. Transient overexpression of the LcPOD4 gene in tomato and litchi fruits significantly enhanced POD activity and total phenolic and flavonoid contents while accelerating peel color change in the fruit. Collectively, our results indicate that LcPOD4 may contribute, at least partially, to the enhancement of antioxidant capacity in litchi fruit but does not retard peel browning and senescence.

Post-shooting sprays of nutrients for improving fruit quality, antioxidant properties and shelf-life in banana (Musa sp.)

An experiment was conducted during 2018–21 at the research farms of Kittur Rani Channamma College of Horticulture (University of Horticultural Sciences, Bagalkot, Karnataka), Arabhavi, Karnataka to study the effect of post-shooting sprays of nutrients for improving fruit quality, antioxidant properties and shelf-life in banana (Musa sp.). Effects of potassium sulphate (SOP) @20 g/L and micro-nutrients, viz. customised micronutrient mix Arka Banana SpecialTM @5 g/L, zinc sulphate @1 g/L, boric acid @ 2 g/L, ferrous sulphate- EDTA @3 g/L and copper sulphate @2 g/L sprays in different combinations imposed at post-shooting stage were evaluated in terms of fruit quality and shelf-life after ripening in banana cv. Grand Naine. Treatment comprising of SOP @20 g/L and Arka Banana SpecialTM @5 g/L improved pulp TSS (22.300B), TSS: TA ratio (71.26), fruit firmness (5.16 lb), MSI (18.12%) and peroxidase (POD) activity (15.98ΔA470/min/g). While polyphenol oxidase (PPO) activity (120.42 U/ mg protein), peel browning index (1.42), fruit weight loss (12.73%) and titratable acidity (0.31%) were declined. An increase in green life (8.22 days) and yellow life (3.93 days) of fruits by potassium application, enhancing the storage and shelf-life of the fruits. Pulp TSS was positively correlated with total sugars (0.938**), TSS: acid ratio (0.981**), shelf-life (0.955**), fruit firmness (0.931**) and MSI (0.921**), and negatively correlated with TA (-0.980**) and PPO activity (-0.967**).

Effects of 1–MCP Treatment on Postharvest Fruit of Five Pomegranate Varieties during Low-Temperature Storage

Pomegranate fruit production and consumption are restricted by appropriate postharvest handling practices. 1–MCP (1–methylcyclopropene) is a natural preservative of fruits and vegetables; however, its effects on the storage of different pomegranate varieties have not been extensively investigated. Herein, the effects of 1.0 μL L−1 1–MCP on postharvest pomegranate fruit of three soft-seed ‘Mollar’, ‘Malisi’, and ‘Tunisan soft seed’ and two semi-soft-seed ‘Moyuruanzi’ and ‘Dongyan’ were investigated over 90 d (days) under low-temperature storage at 4 ± 0.5 °C with a relative humidity of 85–90%. Several indexes of exterior and interior quality were recorded, the sensory quality was evaluated, and the respiration and ethylene production were also determined. The results showed that peel browning was generally more severe in the soft-seed varieties than in the semi-soft-seed varieties. Significantly lighter peel browning presented in the three soft-seed fruits from 45 d after the 1–MCP treatment, with 35%, 19%, and 28% less than those controls at 90 d, correspondingly. However, 1–MCP only significantly decreased peel browning in the semi soft-seed fruits at 60 days. A prominent decrease in weight loss was recorded in all five varieties, with ‘Malisi’ showing the largest and ‘Dongyan’ the smallest difference between the 1–MCP and control treatments. Through the results of color, physiological, and chemical changes, as well as sensory properties, better color and total acceptance were found with higher titratable acids and vitamin C but with decreased anthocyanins in most fruits treated with 1–MCP. In contrast to the control, remarkable suppression of ethylene production peaks in all whole fruits and periodical increase in respiration rates in the soft-seed whole fruits were activated at 30–60 d after storage by the 1–MCP treatment, roughly when peel browning occurred and began increasing. Overall, our findings provided a crucial foundation for extending the application of 1–MCP in postharvest preservation of pomegranates.

Exogenous azacytidine alleviates peel browning of postharvest bananas (Musa acuminata) showing an important role of DNA methylation

Banana fruit is usually harvested unripe and the peel browning is a quality challenge during the post-ripening or senescence with or without exogenous ethylene’s ripening acceleration. Browning can occur during logistics, sales, or domestic storage and largely reduces the economic value and consumer liking. 5-azacytidine (5-azaC) is a DNA methylation inhibitor, which has been recently found important in regulating fruit ripening and quality shaping, but its role remains unknown considering banana browning. Currently, we put bananas in the 10 mmol/L solution of 5-azaC for vacuum infiltration (15 min) and then continuous immersion (30 min), and stored them under controlled-release ethylene for 9 days. This treatment effectively retard peel browning. In the final sampling, there were 9.3 times as many bananas in the control group with severe 20–40% browning as there were in the 5-azaC-treated group. Further analysis demonstrated that the polyphenol oxidase (PPO) activity and programmed cell death (PCD) process were inhibited by 5-azaC with its methylation-inhibiting effects, which also somehow modulated the ethylene sensitivity of peel cells to alleviate senescence-related browning. This study is expected to offer valuable insights into banana anti-browning strategy development.

CaCl2 treatment effectively delays postharvest senescence of passion fruit.

This study aimed to systematically investigate the changes in peel color, physicochemical characteristics, textural properties, and peel ultrastructure between CaCl2-treated and water-soaked passion fruit under short-term storage at room temperature (20°C) for eight days. The fruit peel was further analyzed and compared for the differences in calmodulin (CaM) gene expression between the two groups. The data were analyzed using principal component analysis. The results confirmed that CaCl2 treatment effectively maintained the appearance and color of passion fruit, inhibited peel browning, and improved fruit quality. The treatment had an effect on maintaining the physiological properties of passion fruit parenchyma, effectively delayed the passion fruit senescence, and kept the structural integrity of the fruit peel. The relative expression of PeCaM gene in the CaCl2-treated fruit peels was higher than that of the control peels. The Ca2+ stimulated the relative expression of the PeCaM gene, which delayed the senescence of passion fruit.

Resistance index and browning mechanism of apple peel under high temperature stress

Apples are one of the most important economic crops worldwide. Because of global warming and an aggravation of environmental, abnormally high temperatures occur frequently in fruit-growing season and seriously affect normal fruit growth and reduce fruit quality and yield. We took five-year-old ‘Ruixue’ (Qinfu 1 × Pink Lady; CNA20151469.1) fruits as test materials, and the ambient temperature during fruit development was monitored. The results showed that during the fruit-growing season, especially during the rapid growth stage (July to August), the maximum daily temperature exceeded 30 °C and lasted for more than 40 days. To determine the effects of high temperature stress on the apple fruit resistance, we treated expanding, veraison, and maturity-period fruits at different temperatures. It was found that the fruits of the expanding period showed strong resistance to high temperature stress, whereas during veraison and maturity, fruit resistance to high temperature stress decreased, and the fruit peel browning phenotype appeared. Meanwhile, the content of malonaldehyde (MDA), hydrogen peroxide (H2O2), and superoxide anion (O2.-) in the peel gradually increased with increasing temperature. The content of total phenols, flavanol, and flavonoids in the peel decreased substantially at 45 °C. Moreover, it was found that polyphenol oxidase gene (MdPPO1) was most sensitive to high temperature stress in apple. Furthermore, transient and stable MdPPO1 overexpression significantly promoted peel browning. The transgenic materials were more sensitive to high temperatures, and browning was more severe compared to non-genetically modified organism (WT). Stable MdPPO1 knockout calli obtained via clustered regularly interspersed short palindromic repeats (CRISPR/Cas9) gene knockout technology reduced the browning phenotype, and the resultant fruits were not sensitive to the effects of high temperature stress. Thus, MdPPO1 expression may be a key factor of high temperature–related changes observed in the browning phenotype that provides a scientific theoretical basis for the selection of high temperature–resistant varieties and apple cultivation and management in the future.

Hot water treatment alleviates peel browning in oriental melons through cutin biosynthesis: A comprehensive metabolomics approach

Peel browning is a significant postharvest issue that affects the marketability of oriental melons. This study aimed to investigate the impact of hot water (HW) treatment on peel browning and metabolites in oriental melons during cold storage and retail conditions. The results revealed that HW treatment effectively reduced the browning index and upregulated the gene expression of heat shock proteins (HSPs) and lipoxygenase, known to play crucial roles in stress responses under chilled condition and browning. Additionally, HW treatment induced the expression of cuticle-related genes, CERs and LACS, particularly under retail conditions at 20 °C after cold storage, resulting in a thicker cuticle layer in treated fruits compared to non-treated fruits. Metabolomics analysis demonstrated significant impacts of HW treatment on linoleic acid metabolism, cutin, and suberin biosynthesis pathways. Specifically, HW treatment led to a notable increase in the concentration of cutin in HWT45-treated fruits, with a 27% increase at 14 days and a remarkable 54% increase at 14 + 2 days compared to the control group. These findings highlight the association between peel browning in oriental melons and cutin/suberin biosynthesis. HW treatment induces the formation of cutin metabolites, leading to enhanced cuticle deposition and reduced browning. These insights provide a basis for developing effective postharvest treatments to prolong the shelf life and enhance the marketability of oriental melons.

Low temperature-induced regulatory network rewiring via WRKY regulators during banana peel browning.

Banana (Musa spp.) fruits, as typical tropical fruits, are cold sensitive, and lower temperatures can disrupt cellular compartmentalization and lead to severe browning. How tropical fruits respond to low temperature compared to the cold response mechanisms of model plants remains unknown. Here, we systematically characterized the changes in chromatin accessibility, histone modifications, distal cis-regulatory elements, transcription factor binding, and gene expression levels in banana peels in response to low temperature. Dynamic patterns of cold-induced transcripts were generally accompanied by concordant chromatin accessibility and histone modification changes. These upregulated genes were enriched for WRKY binding sites in their promoters and/or active enhancers. Compared to banana peel at room temperature, large amounts of banana WRKYs were specifically induced by cold and mediated enhancer-promoter interactions regulating critical browning pathways, including phospholipid degradation, oxidation, and cold tolerance. This hypothesis was supported by DNA affinity purification sequencing, luciferase reporter assays, and transient expression assay. Together, our findings highlight widespread transcriptional reprogramming via WRKYs during banana peel browning at low temperature and provide an extensive resource for studying gene regulation in tropical plants in response to cold stress, as well as potential targets for improving cold tolerance and shelf life of tropical fruits.

Time-Series Transcriptome Analysis Reveals the Molecular Mechanism of Ethylene Reducing Cold Sensitivity of Postharvest 'Huangguan' Pear.

'Huangguan' pear (Pyrus bretschneideri Rehd) fruit is susceptible to cold, characterized by developing peel browning spots (PBS) during cold storage. Additionally, ethylene pretreatment reduces chilling injury (CI) and inhibits PBS occurrence, but the mechanism of CI remains unclear. Here, we deciphered the dynamic transcriptional changes during the PBS occurrence with and without ethylene pretreatment via time-series transcriptome. We found that ethylene suppressed the cold-signaling gene expression, thereby decreasing the cold sensitivity of the 'Huangguan' fruit. Moreover, the "Yellow" module closely correlated with PBS occurrence was identified via weighted gene co-expression network analysis (WGCNA), and this module was related to plant defense via Gene Ontology (GO) enrichment analysis. Local motif enrichment analysis suggested that the "Yellow" module genes were regulated by ERF and WRKY transcription factors. Functional studies demonstrated that PbWRKY31 has a conserved WRKY domain, lacks transactivation activity, and localizes in the nucleus. PbWRKY31-overexpressed Arabidopsis were hypersensitive to cold, with higher expression levels of cold signaling and defense genes, suggesting that PbWRKY31 participates in regulating plant cold sensitivity. Collectively, our findings provide a comprehensive transcriptional overview of PBS occurrence and elucidate the molecular mechanism by which ethylene reduces the cold sensitivity of 'Huangguan' fruit as well as the potential role of PbWRKY31 in this process.

Study on Characteristics and Lignification Mechanism of Postharvest Banana Fruit during Chilling Injury

The banana is prone to chilling injury (CI) at low temperature and showing a series of chilling symptoms, such as peel browning, etc. Lignification is a response to abiotic stress and senescence, which is an important manifestation of fruits and vegetables during chilling exposure. However, little is known about the lignification of bananas during low-temperature storage. Our study explored the characteristics and lignification mechanism of banana fruits during low-temperature storage by analyzing the changes of chilling symptoms, oxidative stress, cell wall metabolism, microstructures, and gene expression related to lignification. The results showed that CI inhibited post-ripening by effecting the degradation of the cell wall and starch and accelerated senescence by increasing O2- and H2O2 content. For lignification, Phenylalanine ammonia-lyase (PAL) might start the phenylpropanoid pathway of lignin synthesis. Cinnamoyl-CoA reductase 4 (CCR4), cinnamyl alcohol dehydrogenase 2 (CAD2), and 4-coumarate--CoA ligase like 7 (4CL7) were up-regulated to promote the lignin monomer's synthesis. Peroxidase 1 (POD1) and Laccase 3 (LAC3) were up-regulated to promote the oxidative polymerization of lignin monomers. These results suggest that changes of the cell wall structure and cell wall metabolism, as well as lignification, are involved in the senescence and quality deterioration of the banana after chilling injury.

Effect mechanism of freeze–thaw cycles on browning of “Nanguo” pears peel

AbstractFreezing is an effective way to prolong the storage period of “Nanguo” pears, but the pear peel would browning during thawing. The browning mechanism of “Nanguo” pears peel under different freeze–thaw cycles was studied in this paper. The membrane lipid peroxidation products, fatty acid content and related enzyme activities of peel browning during freeze–thaw cycles were determined. The results showed that the browning of ‘Nanguo’ pears peel induced by freeze–thaw cycles might be caused by the increased of lipoxygenase (LOX) activity, the decreased of superoxide dismutase (SOD) activity and the degradation of unsaturated fatty acids. Then destroyed the integrity of cell membrane structure and resulted in the loss of cell partition, thus leading to the browning of “Nanguo” pears peel. This caused polyphenol oxidase (PPO) and peroxide (POD) to came into contact with the phenolic substrate and subsequently oxidized the phenolic to formed a brown polymer, leading to browning.Practical ApplicationsDuring the storage and transportation of frozen fruits and vegetables, freezing–thawing phenomenon occurs frequently due to temperature fluctuation, which affects their frozen quality. Freezing and thawing experiments were used to simulate the storage and transportation process to study the effect mechanism of repeated freezing and thawing on ‘Nanguo’ pears peel browning. The results provided a theoretical basis for maintaining the quality of ‘Nanguo’ pears during storage. And it is beneficial to the industrialized production of frozen pear in northeast China.

Transcriptomic and metabolomic analysis reveals a protein module involved in preharvest apple peel browning.

Peel browning is a natural phenomenon that adversely affects the appearance of fruits. Research on the regulation of browning in apples (Malus × domestica Borkh.) has mainly focused on postharvest storage, while studies at the preharvest stage are relatively rare. Apple is an economically important horticultural crop prone to peel browning during growth, especially when the fruits are bagged (dark conditions). The present study's integrated transcriptomics and metabolomics analysis revealed that preharvest apple peel browning was primarily due to changes in phenolics and flavonoids. The detailed analysis identified MdLAC7's (laccase 7) role in the preharvest apple peel browning process. Transient injection, overexpression, and CRISPR/Cas9 knockout of the MdLAC7 gene in apple fruit and calli identified vallinic acid, anthocyanidin, tannic acid, sinapic acid, and catechinic acid as its catalytic substrates. In addition, yeast one-hybrid assay, electrophoretic mobility shift assay, luciferase reporter assay, and ChIP-PCR analysis revealed that MdWRKY31 binds to the promoter of MdLAC7 and positively regulates its activity to promote peel browning of bagged fruits (dark conditions). Interestingly, upon light exposure, the light-responsive transcription factor MdHY5 (ELONGATED HYPOCOTYL 5) bound to the promoter of MdWRKY31 and inhibited the gene's expression, thereby indirectly inhibiting the function of MdLAC7. Subsequent analysis showed that MdHY5 binds to the MdLAC7 promoter at the G-box1/2 site and directly inhibits its expression in vivo. Thus, the study revealed the MdLAC7-mediated mechanism regulating preharvest apple peel browning and demonstrated the role of light in inhibiting MdLAC7 activity and subsequently reducing peel browning. These results provide theoretical guidance for producing high-quality apple fruits.

Browning in Relation to Enzymatic Activities and Phytochemical Content in Terap Peel (Artocarpus odoratissimus Blanco) during Postharvest Ripening

Enzymatic browning is a common limiting factor in the fruit industry because it causes significant losses through fresh product deterioration, affecting taste, flavor, and nutrition. Artocarpus odoratissimus, locally known as terap, is an exotic indigenous fruit to Borneo. This fruit remains underutilized due to its perishability, short shelf-life, and peel browning. Currently, no information has apparently been published on the browning mechanisms of A. odoratissimus. Thus, the present study aims to evaluate the degree of browning and enzymatic activities in relation to the phytochemical contents in A. odoratissimus during postharvest ripening. The experimental design consists of packaging (without packaging and with packaging) and storage temperatures (ambient at 25 °C, and cold storage at 10 °C), which were arranged in a randomized complete block design. Findings showed significantly higher weight loss in fruit stored at 25 °C on days 4 (T1) at 12.20 ± 0.19% and 8 (T5) at 11.09 ± 0.24%. The degree of browning was higher in the fruits stored with packaging at 25 °C, collected on day 4 at 0.48 ± 0.01 and day 8 at 0.51 ± 0.02, and consequently, the phenylalanine ammonia-lyase (671.00 ± 5.25 UE g−1 min−1) and polyphenol oxidase (670.00 ± 2.56 UE g−1 min−1) enzymatic activities were also higher. The lower enzymatic activities were recorded in the fruit stored at 10 °C without packaging, resulting in the least degree of browning. The fruit with the lowest enzymatic activities was stored at 10 °C without packaging, resulting in the least amount of browning. This trend is supported by lower total phenolic content (TPC) and is explained by a strong positive correlation between TPC and PAL (r = 0.927). Low-temperature storage was effective in reducing the effect of browning and deterioration on A. odoratissimus for up to 16 days. The results not only provided insights into the peel browning in A. odoratissimus but also guidance on controlling postharvest fruit browning.

Pre-storage oxalic acid treatment inhibits postharvest browning symptoms and maintains quality of abiu (Pouteria caimito) fruit

The effect of exogenous oxalic acid (OA) treatment on browning and postharvest quality of abiu fruit was evaluated during the storage period. Abiu fruit was soaked in water (control), 5 mM oxalic acid (OA5), and 10 mM oxalic acid (OA10) for 10 min and air-dried, and then stored in an ambient room (28 ± 1 °C and 80 ± 5% RH) for 12 days. The results showed the peel browning in control, and the OA5-treated reached 30% on day-6 of the storage and day-12 storage for the OA10-treated. In addition, the browning symptoms in abiu pulp reached 30% on day-3, day-6, and day-9 storage, for control, OA5, and OA10, respectively. The exogenous OA10 treatment in abiu fruit could suppress the oxidation of phenolic compounds and inhibit an increase in polyphenol oxidase (PPO) enzyme activity and malondialdehyde (MDA) content during storage. In addition, applying the OA10-treated in abiu fruit could reduce 1-aminocyclopropane-1-carboxylic (ACC) concentration, ethylene production, respiration rate, and delay the occurrence of the climacteric peak. The exogenous OA10 treatment in abiu fruit could also reduce fresh weight loss, titratable acidity (TA), ascorbic acid, and maintain fruit firmness during storage. Therefore, the exogenous OA10 treatment could be considered an appropriate treatment to delay browning and preserve the quality of the abiu fruit.